Problems arise when using slide projectors, and similar equipment, to project images onto screens in large halls, such as university lecture theatres and the like. In large halls, the slide projectors are generally located a considerable distance from the screen, so that small adjustments to the alignment of the slide projector are magnified and translate into much larger movements of the projected image on the screen. To align the image properly, requires careful adjustment and aiming which is done by rotating, tilting and yawing the slide projector. Most projectors have adjustable legs for that purpose but they are crude and wobbly and cannot prevent misalignment when the projector gets bumped or nudged.
In order to solve the above problem, the inventors of the invention to be described hereinafter, looked at various existing devices which provide swivel links/orientation devices which they believed might be suitable for use in orienting and aligning slide projectors and the like. However, while many of the devices which provided swivelling with clamping/locking had good locking capabilities, they could not be finely adjusted while being partially clamped. In other devices with good adjusting properties the locking was insufficiently strong and reliable. Many of the existing devices were also over-complicated and in some cases correspondingly expensive due to their providing movement and clamping about three orthogonal axes.
A typical swivel mechanism utilises one axle per axis, requiring one locking mechanism per axis such as in a typical camera tripod, and while this system is functional, it requires adjustment of three different clamps for adjustment in three different axes.
Another prior art device is a theatre light mounting. That device comprises a spherical member coated with a deformable soft plastic. The member is fitted into a concave mating socket which has truncated spikes protruding inwards. When the device is clamped, the spikes are pressed into the plastic. This device holds its orientation well. However, the plastic retains the spike depressions for a long time and this makes the device unsuitable for quick re-alignment. Also, it is difficult to make slight adjustments with this device.
Similar problems exist with stands and mounts for mounting large speakers.
It is an object of the present invention to alleviate the problems of the existing orientation devices described above.